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BY THE NUMBERS //

Joint Replacement: Baked-In Strength

Artificial hips and knees must endure great stress, so researchers at MGH’s Harris Orthopaedic Laboratory created a more durable version.

By Brandon Keim // The MGH Research Issue 2011
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600
Pounds of force exerted per step on a 200-pound person’s hip

3 million
Steps an average active 50-year-old takes in one year

31,536,000
Steps taken in one year by one hip simulator at MGH’s Harris Orthopaedic Laboratory, used to predict how artificial joints will respond to extended use

1970s
First recognition by MGH orthopedic surgeon William Harris of the phenomenon of smooth polyethylene joints shedding small particles, causing bone deterioration

1998
First implant of a joint made of highly cross-linked polyethylene, which proved more durable than smooth polyethylene

30
Atoms in a molecule of candle wax, a compound structurally similar to ultrahigh-molecular-weight highly cross-linked polyethylene

1,071,428
Atoms in a molecule of ultrahigh-molecular-weight polyethylene before it is cross-linked, resulting in its exceptional durability

248
Degrees Fahrenheit at which vitamin E, which counters the free radicals that can break down a joint, diffuses into the polyethylene

5,000
People implanted with MGH-developed highly cross-linked polyethylene hip joints every day

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